Typical fields of application of generic round-shaft chisel arrangements are especially the equipment of milling drums for cold milling machines, recyclers and surface miners. Such machines are known, for example, from the specifications DE 10 2011 114 185 A1 and DE 10 2010 014 529 A1 for a cold milling machine, from DE 10 2010 014 904 A1 for a recycler, and DE 10 2012 216 262 B3 for a surface miner. Essential elements in such a round-shaft chisel arrangement are a chisel with a cylindrical chisel shaft extending along the longitudinal axis and a chisel tip which represents the working tool of the chisel. The chisel tip is connected to the chisel shaft, especially in a direct fashion. The chisel tip frequently further comprises respective hard-metal tips or comparable devices in order to further increase the wear resistance of the chisel. In working operation, such chisels are inserted into suitable chisel holders which produce a connection between the chisel and the milling drum. Such chisel holders are described, for example, in the specifications DE 10 2010 051 048 A1 and DE 10 2010 044 649 A1, to which reference is made hereby. The used chisel holders usually have a base region with which the chisel holder is connected to the supporting tube of the milling drum. The chisel holder further comprises a retaining recess, which is especially shaped like a hollow cylinder at least in relevant parts, and into which the round-shaft chisel protrudes with its chisel shaft and in which it is retained during the working process. A device for the releasable fixing of a round-shaft chisel in a chisel bushing with a fixing ring with a circumferential rib engaging in a circumferential annular groove is known from AT 004 193 U1.
It is necessary for a reliable working process that the positioning of the chisel, especially in the axial direction of the chisel shaft, in the chisel holder or within its retaining recess is ensured. A so-called clamping sleeve is frequently used in the prior art, which in the delivery state is pretensioned, e.g., by means of a wear disc which is provided to enclose the chisel shaft. If the entirety of the chisel and the clamping sleeve is seated in the chisel holder, the clamping sleeve is relaxed and rests at least in sections on the inner jacket surface of the receiving borehole in the chisel holder for the round-shaft chisel. In working operation of the round-shaft chisels, it is now provided that the round-shaft chisel is rotatably accommodated in the retainer of the chisel holder in order to enable constant, rotational-symmetric wear and tear of the chisel. In order to ensure the rotatability of the chisel around the longitudinal axis of the round-shaft chisel and to simultaneously ensure axial securing of the round-shaft chisel in the clamping sleeve, the clamping sleeve comprises punched-out retaining tabs which engage in a radially inwardly directed fashion in a retaining groove (retaining bead) surrounding the circumference of the chisel shaft. Such an arrangement is known from DE 20 2006 020 765 U1, for example. As a result, the round-shaft chisel is secured in its axial position against displacement by the retaining tabs engaging in the retaining groove on the one hand. On the other hand, a rotational bearing for the round-shaft chisel is obtained, so that it is able to rotate in the retainer about its longitudinal axis. In practical operation of such an arrangement, it has been noticed, however, that it is relatively susceptible to the penetration of considerable quantities of milled material mixed with water, as a result of which the rotatability and thus uniform wear and tear of the round-shaft chisel are impaired. This is especially the case when a kind of interlocking connection is achieved between the clamping sleeve and the round-shaft chisel by the introduced milling material, so that the rotatability of the round-shaft chisel thus ceases completely.
An alternative to the aforementioned known clamping sleeves is disclosed, for example, in DE 10 2011 054 386 A1, in which a short, spring-elastic ring is present which is carried by a groove in the chisel shaft, and which comprises several fastening sections distributed over its circumference, which in the clamped state rest either directly on the smooth surface of the chisel holder borehole or in a respective bead. This arrangement partly provides unsatisfactory retaining results of the round-shaft chisel in the respective receiving borehole and the rotational behaviour of the chisel is thus frequently not ensured in the desired manner. Furthermore, considerable quantities of milled material can penetrate the intermediate space between the chisel shaft and the inner wall of the retaining recess.